U.S. patent number 10,167,053 [Application Number 15/345,387] was granted by the patent office on 2019-01-01 for bicycle drive unit.
This patent grant is currently assigned to Shimano Inc.. The grantee listed for this patent is Shimano Inc.. Invention is credited to Takashi Yamamoto.
United States Patent |
10,167,053 |
Yamamoto |
January 1, 2019 |
Bicycle drive unit
Abstract
A bicycle drive unit has a transmission and a motor that
transmits torque to the transmission. The transmission includes
first and second input side rotating bodies, first and second
output side rotating bodies, an output unit and a switching
mechanism. The first and second output side rotating bodies are
coupled to the first and second input side rotating bodies,
respectively. The switching mechanism switches between a first
state in which rotation of the first input side rotating body is
transmitted to the output unit, and a second state in which
rotation of the second input side rotating body is transmitted to
the output unit. Only torque of the motor is transmitted from the
first and second input side rotating bodies to the output unit,
while torque outputted from the output unit merges with a manual
drive force in a drive force transmission path from the output unit
to a wheel.
Inventors: |
Yamamoto; Takashi (Osaka,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shimano Inc. |
Sakai, Osaka |
N/A |
JP |
|
|
Assignee: |
Shimano Inc. (Osaka,
JP)
|
Family
ID: |
58693369 |
Appl.
No.: |
15/345,387 |
Filed: |
November 7, 2016 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
|
US 20170152001 A1 |
Jun 1, 2017 |
|
Foreign Application Priority Data
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|
|
|
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Nov 27, 2015 [JP] |
|
|
2015-231987 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B62M
6/55 (20130101); B62M 11/06 (20130101); F16H
3/10 (20130101) |
Current International
Class: |
B62M
6/55 (20100101); F16H 3/10 (20060101); B62M
11/06 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
2623419 |
|
Jun 1997 |
|
JP |
|
4056130 |
|
Mar 2008 |
|
JP |
|
6523636 |
|
Jun 2014 |
|
JP |
|
WO-2015008314 |
|
Jan 2015 |
|
WO |
|
Primary Examiner: Hurley; Kevin
Assistant Examiner: Stabley; Michael R
Attorney, Agent or Firm: Global IP Counselors, LLP
Claims
What is claimed is:
1. A bicycle drive unit comprising: a transmission having a
plurality of gear shift stages; and a motor configured to transmit
torque to the transmission, the transmission comprises a first
input side rotating body and a second input side rotating body
rotatably disposed around a first rotational axis; a first output
side rotating body rotatably disposed around a second rotational
axis that is parallel to the first rotational axis, and coupled to
the first input side rotating body; a second output side rotating
body rotatably disposed around the second rotational axis and
coupled to the second input side rotating body; an output unit
configured to receive rotation of the first output side rotating
body and the second output side rotating body; and a switching
mechanism configured to switch between a first state in which the
rotation of the first input side rotating body is transmitted to
the output unit, and a second state in which the rotation of the
second input side rotating body is transmitted to the output unit;
the output unit being configured to receive only torque from the
motor via the first input side rotating body and the second input
side rotating body, and the output unit being configured such that
torque outputted from the output unit merges with a manual drive
force in a drive force transmission path from the output unit to a
wheel.
2. The bicycle drive unit according to claim 1, wherein the output
unit includes a crankshaft.
3. The bicycle drive unit according to claim 1, wherein the output
unit includes a hollow shaft configured to receive a crankshaft
therein.
4. The bicycle drive unit according to claim 3, further comprising
the crankshaft being coupled to the hollow shaft of the output
unit.
5. The bicycle drive unit according to claim 1, wherein the first
input side rotating body and the second input side rotating body
are gears having different diameters; the first output side
rotating body is a gear that is engaged with the first input side
rotating body; and the second output side rotating body is a gear
that is engaged with the second input side rotating body.
6. The bicycle drive unit according to claim 1, further comprising
a first rotational shaft that rotates on the first rotational axis,
the first output side rotating body and the second output side
rotating body being fixed to the output unit; and the switching
mechanism integrally rotating the first rotational shaft and the
first input side rotating body together as a unit and rotating the
first rotational shaft relative to the second input side rotating
body while the switching mechanism is in the first state, and the
switching mechanism integrally rotates the first rotational shaft
and the second input side rotating body together as a unit and
rotating the first rotational shaft relative to the first input
side rotating body while the switching mechanism is in the second
state.
7. The bicycle drive unit according to claim 6, wherein a
rotational speed ratio of the first output side rotating body with
respect to a rotational speed of the first input side rotating body
is configured to be smaller than a rotational speed ratio of the
second output side rotating body with respect to a rotational speed
of the second input side rotating body; and the switching mechanism
comprises: a connection switching unit configured to couple the
first rotational shaft and the second input side rotating body
while the switching mechanism is in the first state and allow a
relative rotation between the first rotational shaft and the second
input side rotating body while the switching mechanism is in the
second state, and a one-way clutch disposed between the first
rotational shaft and the first input side rotating body.
8. The bicycle drive unit according to claim 7, wherein the one-way
clutch is configured to integrally rotate the first rotational
shaft and the first input side rotating body while the rotational
speed of the first input side rotating body in a first rotational
direction is equal to the rotational speed of the first rotational
shaft, and the one-way clutch is configured to rotate the first
rotational shaft relative to the first input side rotating body
while the rotational speed of the first input side rotating body in
the first rotational direction is greater than the rotational speed
of the first rotational shaft.
9. The bicycle drive unit according to claim 7, wherein the
connection switching unit comprises a pawl provided on and
protruding from one of the first rotational shaft and the second
input side rotating body, and an engagement portion provided to the
other of the first rotational shaft and the second input side
rotating body so that the pawl is configured to selectively engage
the engagement portion, and the first rotational shaft and the
second input side rotating body are coupled by the pawl engaging
the engagement portion, and permitting rotation of the first
rotational shaft with respect to the second input side rotating
body by disengaging the pawl from the engagement portion.
10. The bicycle drive unit according to claim 7, wherein the
switching mechanism further comprises an actuator configured to
control the connection switching unit.
11. The bicycle drive unit according to claim 10, wherein the
connection switching unit comprises a pawl provided on and
protruding from one of the first rotational shaft and the second
input side rotating body, and an engagement portion provided to the
other of the first rotational shaft and the second input side
rotating body so that the pawl is configured to selectively engage
the engagement portion, the first rotational shaft and the second
input side rotating body are coupled by the pawl engaging the
engagement portion, and permitting rotation of the first rotational
shaft with respect to the second input side rotating body by
disengaging the pawl from the engagement portion, and the actuator
comprises a biasing member that applies force to the pawl so that
the pawl projects from one of the first rotational shaft and the
second input side rotating body; a movable member that is
configured to cause the pawl to operate with respect to the other
of the first rotational shaft and the second input side rotating
body so that the pawl moves away from the engagement portion; and a
drive unit that switches between the first state arid the second
state by moving the movable member.
12. The bicycle drive unit according to claim 6, wherein the first
rotational shaft is inserted in holes provided in each of the first
input side rotating body and the second input side rotating
body.
13. The bicycle drive unit according to claim 12, wherein the
connection switching unit comprises a pawl provided on and
protruding from one of the first rotational shaft and the second
input side rotating body, and an engagement portion provided to the
other of the first rotational shaft and the second input side
rotating body so that the pawl is configured to selectively engage
the engagement portion, the first rotational shaft and the second
input side rotating body are coupled by the pawl engaging the
engagement portion, and permitting rotation of the first rotational
shaft with respect to the second input side rotating body by
disengaging the pawl from the engagement portion, and the pawl is
disposed between an outer perimeter of the first rotational shaft
and an inner perimeter of the second input side rotating body.
14. The bicycle drive unit according to claim 1, further comprising
a speed reducer configured to reduce a rotational speed of the
motor and transmit a rotation of the motor to the transmission.
15. The bicycle drive unit according to claim 1, wherein the motor
is partially disposed on a plane that includes at least one of the
first input side rotating body and the second input side rotating
body, the plane being perpendicular to the first rotational axis
and the second rotational axis.
16. The bicycle drive unit according to claim 1, wherein the first
output side rotating body and the second output side rotating body
are integrally fanned together as a unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No.
2015-231987, filed on Nov. 27, 2015.The entire disclosure of
Japanese Patent Application No. 2015-231987 is hereby incorporated
herein by reference.
BACKGROUND
Field of the Invention
The present invention relates to a bicycle drive unit.
Background Information
Some bicycles are provided with a bicycle drive unit to assist the
rider by generating an auxiliary drive force. A bicycle drive unit
comprises a motor for assisting the manual drive force. In addition
to the motor, the bicycle drive unit often further comprises a
reduction gear that decelerates and outputs the rotation of the
motor, an output unit to which rotation is transmitted from each of
the reduction gear and a crankshaft, and the like. One example of
such a conventional bicycle drive unit is disclosed in Japanese
Patent No. 2,623,419.
SUMMARY
Generally, the present disclosure is directed to various features
of a bicycle drive unit. In a conventional bicycle drive unit, the
rotational speed of the motor is proportional to the rotational
speed of the crank. Since the motor has a characteristic in which
the output torque varies according to the rotational speed, there
is the risk that the output torque of the motor will be
insufficient, thereby reducing the assisting force, depending on
the rotational speed of the crank.
One object of the present invention is to provide a bicycle drive
unit that can prevent a reduction in the assisting force
accompanying a change in the rotational speed of the crank.
In view of the state of the known technology and in accordance with
a first aspect of the present disclosure, a bicycle drive unit
according to the present invention comprises a transmission having
a plurality of gear shift stages and a motor configured to transmit
torque to the transmission. The transmission comprises a first
input side rotating body, a second input side rotating body, a
first output side rotating body, a second output side rotating
body, an output unit and a switching mechanism. The second input
side rotating body is rotatably disposed around a first rotational
axis. The first output side rotating body is rotatably disposed
around a second rotational axis that is parallel to the first
rotational axis and is coupled to the first input side rotating
body. The second output side rotating body is rotatably disposed
around the second axis and is coupled to the second input side
rotating body. The output unit is configured to receive rotation of
the first output side rotating body and the second output side
rotating body. The switching mechanism is configured to switch
between a first state in which the rotation of the first input side
rotating body is transmitted to the output unit, and a second state
in which the rotation of the second input side rotating body is
transmitted to the output unit. The output unit is configured to
receive only torque of the motor being transmitted from the first
input side rotating body and the second input side rotating body to
the output unit. The output unit is configured such that torque
that is output from the output unit merges with a manual drive
force in a drive force transmission path from the output unit to a
wheel.
According to one example of the bicycle drive unit, the output unit
includes a crankshaft.
According to one example of the bicycle drive unit, the output unit
includes a hollow shaft configured to receive a crankshaft
therein.
One example of the bicycle drive unit further comprises the
crankshaft being coupled to the output unit.
According to one example of the bicycle drive unit, the first input
side rotating body and the second input side rotating body are
gears having different diameters. The first output side rotating
body is a gear that is engaged with the first input side rotating
body. The second output side rotating body is a gear that is
engaged with the second input side rotating body.
One example of the bicycle drive unit further comprises a first
rotational shaft that rotates on the first rotational axis. The
first output side rotating body and the second output side rotating
body are fixed to the output unit. The switching mechanism is
configured to switch between a first state and a second state. The
switching mechanism integrally rotates the first rotational shaft
and the first input side rotating body together as a unit and
rotates the first rotational shaft relative to the second input
side rotating body while the switching mechanism is in the first
state. The switching mechanism integrally rotates the first
rotational shaft and the second input side rotating body as a unit
and rotates the first rotational shaft relative to the first input
side rotating body while the switching mechanism is in the second
state.
According to one example of the bicycle drive unit, a rotational
speed ratio of the first output side rotating body with respect to
a rotational speed of the first input side rotating body is
configured to be smaller than a rotational speed ratio of the
second output side rotating body with respect to a rotational speed
of the second input side rotating body. The switching mechanism
comprises a connection switching unit and a one-way clutch. The
connection switching unit is configured to couple the first
rotational shaft and the second input side rotating body while the
switching mechanism is in the first state and allow a relative
rotation between the first rotational shaft and the second input
side rotating body while the switching mechanism is in the second
state. The one-way clutch is provided between the first rotational
shaft and the first input side rotating body.
According to one example of the bicycle drive unit, the one-way
clutch is configured to integrally rotate the first rotational
shaft and the first input side rotating body while the rotational
speed of the first input side rotating body in a first rotational
direction is equal to the rotational speed of the first rotational
shaft. The one-way clutch is configured to rotate the first
rotational shaft relative to the first input side rotating body
while the rotational speed of the first input side rotating body in
the first rotational direction is greater than the rotational speed
of the first rotational shaft.
According to one example of the bicycle drive unit, the connection
switching unit comprises a pawl and an engagement portion. The pawl
is provided on and protruding from one of the first rotational
shaft and the second input side rotating body. The engagement
portion is provided to the other of the first rotational shaft and
the second input side rotating body so that the pawl is configured
to selectively engage the engagement portion. The first rotational
shaft and the second input side rotating body are coupled by the
pawl engaging the engagement portion, and permitting rotation of
the first rotational shaft with respect to the second input side
rotating body by disengaging the pawl from the engagement
portion.
According to one example of the bicycle drive unit, the switching
mechanism further comprises an actuator configured to control the
connection switching unit.
According to one example of the bicycle drive unit, the actuator
comprises a biasing member, a movable member and a drive unit. The
biasing member applies a force to the pawl so that the pawl
projects from one of the first rotational shaft and the second
input side rotating body. The movable member that is configured to
cause the pawl to operate with respect to the other of the first
rotational shaft and the second input side rotating body so that
the pawl moves away from the engagement portion. The drive unit
switches between the first state and the second state by moving the
movable member.
According to one example of the bicycle drive unit, the first
rotational shaft is inserted in holes provided in each of the first
input side rotating body and the second input side rotating
body.
According to one example of the bicycle drive unit, the pawl is
disposed between an outer perimeter of the first rotational shaft
and an inner perimeter of the second input side rotating body.
One example of the bicycle drive unit further comprises a speed
reducer configured to reduce a rotational speed of the motor and
transmit the rotational speed of the motor to the transmission.
According to one example of the bicycle drive unit, the motor is
partially is disposed on a plane as at least that includes one of
the first input side rotating body and the second input side
rotating body. The plane is perpendicular to the first rotational
axis and the second rotational axis.
According to one example of the bicycle drive unit, the first
output side rotating body and the second output side rotating body
are integrally formed together as a unit.
The bicycle drive unit of the present invention is configured to
prevent a reduction in the assisting force accompanying a change in
the rotational speed of the crank.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the attached drawings which form a part of this
original disclosure.
FIG. 1 is a side elevational view of a drivetrain of an
electrically assisted bicycle equipped with a bicycle drive unit in
accordance with a first embodiment.
FIG. 2 is a cross-sectional view of the bicycle drive unit as seen
along section line 2-2 in FIG. 1, when the switching mechanism is
in the first state.
FIG. 3 is a cross-sectional view of the bicycle drive unit as seen
along section line 2-2 in FIG. 1, when the switching mechanism is
in the second state.
FIG. 4 is a cross-sectional view of the bicycle drive unit in
accordance with one modification.
DETAILED DESCRIPTION OF EMBODIMENTS
Selected embodiments will now be explained with reference to the
drawings. It will be apparent to those skilled in the bicycle field
from this disclosure that the following descriptions of the
embodiments are provided for illustration only and not for the
purpose of limiting the invention as defined by the appended claims
and their equivalents.
An electrically assisted bicycle 10 shown in FIG. 1 comprises a
bicycle drive unit (hereinafter referred to as "drive unit 30") in
accordance with a first embodiment. In one example, the
electrically assisted bicycle 10 further comprises a pair of crank
arms 12, a pair of pedals 16, a front sprocket 18, a rear sprocket
20, a chain 22 and a first clutch 24.
The crank arms 12 are coupled to the opposite ends of a crankshaft
32 in a state of being integrally rotatable with the crankshaft 32
of the drive unit 30. The crank arms 12 together with the
crankshaft 32 form a crank. The pedals 15 each comprises a pedal
main body 17 and a pedal shaft 14. The pedal shafts 14 are coupled
to the crank arms 12, respectively. The pedal main bodies 17 are
supported on the pedal shafts 14, respectively, in a state of being
rotatable with respect to the pedal shafts 14.
The front sprocket 18 is coupled with the drive unit 30 via an
output unit 58 of the drive unit 30. The rear sprocket 20 is
coupled with a rear wheel (not shown) of the electrically assisted
bicycle 10 via the first clutch 24. The first clutch 24 is a
one-way clutch that transmits the rotation of the front sprocket 18
to the rear wheel and that does not transmit the rotation of the
rear wheel to the front sprocket 18. The chain 22 is engaged with
the front sprocket 16 and the rear sprocket 20.
The function of the drive unit 30 is to assist the manual drive
force that is inputted to the crankshaft 32. The drive unit 30 is
mounted on a frame of the electrically assisted bicycle 10 and is
detachable with respect to the frame. An example of a means to join
the drive unit 30 and the frame are bolts. A battery (not shown) is
mounted on the frame of the electrically assisted bicycle 10. The
battery (not shown) is configured to supply electrical energy to
the drive unit 30.
As shown in FIG. 2, the drive unit 30 comprises a transmission 36
and a motor 38. One example of a motor 38 is an electric motor. In
one example, the drive unit 30 further comprises a crankshaft 32, a
second clutch 34, a housing 40, a first rotational shaft 42, a
speed reducer 44 and a controller 46.
The crankshaft 32 is supported by the drive unit 30 in a state of
being rotatable with respect to the drive unit 30. Both ends of the
crankshaft 32 protrude from the housing 40. The transmission 36,
the motor 38, the crankshaft 32, the second clutch 34, the housing
40, the first rotational shaft 42, the speed reducer 44 and the
controller 46 are provided in the housing 40. The controller 46 is
programmed to execute a control program that is set in advance. The
controller 46 comprises a processor, for example, a CPU (Central
Processing Unit) or an MPU (Micro Processing Unit). The controller
46 preferably includes a memory device for storing programs and
data.
The crankshaft 32 is coupled to the output unit 58 of the
transmission 36 via the second clutch 34. One end 58A of the output
unit 58 protrudes from the housing 40. The crankshaft 32 is
inserted in the output unit 58 so that both ends protrude from the
output unit 58 and the housing 40. The crankshaft 32 is supported
in the housing 40 via the output unit 58.
The second clutch 34 is provided between the outer perimeter of the
crankshaft 32 and the inner perimeter of the output unit 58. The
second clutch is a one-way clutch. The second clutch 34 transmits
rotation from the crankshaft 32 to the output unit 58 while the
crankshaft 32 is rotated forward. The second clutch 34 is coupled
with the crankshaft 32 and the output unit 58 so as to not transmit
rotation from the crankshaft 32 to the output unit 58 while the
crankshaft 32 is rotated rearward.
The front sprocket 18 is arranged on the side of the housing 40 and
located outside of the housing 40. The front sprocket 18 is
attached to the drive unit 30 by a bolt B. The bolt B is threaded
to the output unit 58 so as to fix the front sprocket 18 between
the output unit 58 and the bolt B.
When a manual drive force is inputted to the pedals 16 in a forward
direction to rotate the crankshaft 32 as shown in FIG. 1, the
crankshaft 32 is also rotated forward with respect to the frame of
the electrically assisted bicycle 10. In this case, the rotation of
the crankshaft 32 is transmitted to the front sprocket 18 via the
second clutch 34 and the output unit 58, and the rotation of the
front sprocket 18 is transmitted to the rear sprocket 20 via the
chain 22. When a manual drive force is inputted to the pedals 16 in
a rearward direction to rotate the crankshaft 32, the crankshaft 32
is also rotated rearward with respect to the frame. In this case,
the rotation of the crankshaft 32 is not transmitted to the output
unit 58 and the front sprocket 18 by the action of the second
clutch 34.
As shown in FIG. 2, the speed reducer 44 is configured to reduce
the rotational speed of the motor 38 and transmits the rotation of
the motor 38 to the transmission 36. The speed reducer 44 comprises
a first rotational shaft 42 and a second rotational shaft 48. The
first rotational shaft 42 rotates on a first rotational axis CA.
The first rotational shaft 42 is rotatably supported in the housing
40. The first rotational shaft 42 is supported in the housing 40
via a plurality of bearings provided at intervals along the axial
direction. The first rotational axis CA is provided away from a
second rotational axis CB and parallel to the second rotational
axis CB. The second rotational shaft 48 is rotatably supported in
the housing 40 and provided in a position adjacent to the output
shaft 38A of the motor 38. The second rotational shaft 48 is
provided parallel to the first rotational shaft 42 and away from
the first rotational shaft 42. The second rotational shaft 48 is
rotatably supported in the housing 40 via a plurality of bearings
provided at intervals in the axial direction.
The motor 38 is configured to transmit torque to the transmission
36. The motor 38 is partially disposed on the same plane as at
least one of the first input side rotating body 50 and the second
input side rotating body 52. This plane is perpendicular to the
first rotational axis CA and the second rotational axis CB.
The speed reducer 44 further comprises a gear 38B, a first gear
48A, a second gear 48B and a gear 42A. The gear 38B is provided on
the output shaft 38A of the motor 38. The first gear 48A and the
second gear 48B are provided on the second rotational shaft 48. The
gear 42A is provided on the first rotational shaft 42. The first
gear 48A is coaxially arranged with the second rotational shaft 48,
which is integrally rotated with the first gear 48A. The first gear
48A is engaged with the gear 38B. The total number of teeth of the
gear 38B is less than the total number of teeth of the first gear
48A. Accordingly, the rotation of the motor 38 is decelerated and
transmitted to the second rotational shaft 48. The second gear 48B
is provided on a portion of the second rotational shaft 48 that is
different from the portion to which is provided the first gear 48A.
The second gear 48B is coaxial with the second rotational shaft 48
and fixed to the second rotational shaft 48. Thus, the second gear
48B integrally rotates with the second rotational shaft 48. The
second gear 48B is engaged with the gear 42A. The total number of
teeth of the second gear 48B is less than the total number of teeth
of the gear 42A. Accordingly, the rotation of the second rotational
shaft 48 is decelerated and transmitted to the first rotational
shaft 42. The gear 38B can be formed integrally with the output
shaft 38A of the motor 38, or can be formed separately and coupled
thereto. At least one of the first gear 48A and the second gear 48B
can be formed integrally with the second rotational shaft 48, or
can be formed separately and coupled thereto. The gear 42A can be
formed integrally with the first rotational shaft 42, or can be
formed separately and coupled thereto.
The transmission 36 comprises a plurality of gear shift stages. The
transmission 36 comprises a first input side rotating body 50, a
second input side rotating body 52, a first output side rotating
body 54, a second output side rotating body 56, an output unit 58
and a switching mechanism 60.
The first input side rotating body 50 and the second input side
rotating body 52 are rotatably provided around the first rotational
axis CA. The first input side rotating body 50 and the second input
side rotating body 52 are provided adjacent to each other in the
axial direction of the first rotational shaft 42. The first input
side rotating body 50 and the second input side rotating body 52
are relatively rotatable. The first input side rotating body 50
comprises a gear 50A with a plurality of teeth formed on the outer
perimeter thereof. The second input side rotating body 52 comprises
a gear 52A with a plurality of teeth formed on the outer perimeter
thereof. The first input side rotating body 50 and the second input
side rotating body 52 include the gears 50A and 52A, respectively,
that have different diameters. The diameter of the gear 50A is
smaller than the diameter of the gear 52A. The total number of
teeth of the gear 50A is less than the total number of teeth of the
gear 52A. The first rotational shaft 42 is inserted in holes 50B
and 52B that are respectively provided to the first input side
rotating body 50 and the second input side rotating body 52.
The first output side rotating body 54 is rotatably provided around
the second axis CB. The first output side rotating body 54 is
coupled to the first input side rotating body 50. Specifically, the
first output side rotating body 54 comprises a plurality of teeth
on the outer perimeter. The first output side rotating body 54 is
formed by a gear 54A that is engaged with the first input side
rotating body 50. The gear 50A which forms the first input side
rotating body 50 is engaged with a gear 54A which forms the first
output side rotating body 54. Accordingly, when rotation from the
first rotational shaft 42 is inputted to the first input side
rotating body 50, the first output side rotating body 54 is
rotated.
The second output side rotating body 56 is rotatably provided
around the second axis CB. The second output side rotating body 56
is coupled to the second input side rotating body 52. Specifically,
the second output side rotating body 56 comprises a plurality of
teeth on the outer perimeter. The second output side rotating body
56 is formed by a gear 56A that is engaged with the second input
side rotating body 52. The gear 52A which forms the second input
side rotating body 52 is engaged with a gear 56A which forms the
second output side rotating body 56. Accordingly, when rotation
from the first rotational shaft 42 is inputted to the second input
side rotating body 52, the second output side rotating body 56 is
rotated.
The first output side rotating body 54 and the second output side
rotating body 56 are integrally formed. The diameter of the gear
54A is larger than the diameter of the gear 56A. The total number
of teeth of the gear 54A is greater than the total number of teeth
of the gear 56A. Accordingly, the ratio of the rotational speed of
the first output side rotating body 54 relative to the rotational
speed of the first input side rotating body 50 is configured to be
greater than the ratio of the rotational speed of the second output
side rotating body 56 relative to the rotational speed of the
second input side rotating body 52.
The output unit 58 is a hollow shaft. The crankshaft 32 is disposed
inside the output unit 58. The output unit 58 is provided in the
housing 40 so as to be rotatable around the second axis CB. The
first output side rotating body 54 and the second output side
rotating body 56 are non-rotatably provided on the outer perimeter
of the output unit 58 by, for example, spline fitting, press
fitting, or the like. The first output side rotating body 54 and
the second output side rotating body 56 can be integrally formed
with the output unit 58 during the formation of the output unit 58.
The first output side rotating body 54 and the second output side
rotating body 56 are fixed to the output unit 58. Accordingly, the
rotation of the first output side rotating body 54 and the rotation
of the second output side rotating body 56 are selectively
transmitted to the output unit 58.
The switching mechanism 60 comprises a connection switching unit
62, a one-way clutch 64 and an actuator 66. The switching mechanism
60 is configured to switch between a first state and a second
state. In the first state, the rotation of the first input side
rotating body 50 is transmitted to the output unit 58. In second
state, the rotation of the second input side rotating body 52 is
transmitted to the output unit 58. The switching mechanism 60
causes the first rotational shaft 42 and the first input side
rotating body 50 to be integrally rotatable, and causes the first
rotational shaft 42 and the second input side rotating body 52 to
be relatively rotatable, in the first state. The switching
mechanism 60 causes the first rotational shaft 42 and the second
input side rotating body 52 to be integrally rotatable, and causes
the first rotational shaft 42 and the first input side rotating
body 50 to be relatively rotatable, in the second state.
The connection switching unit 62 connects the first rotational
shaft 42 and the second input side rotating body 52 in the second
state, and permits a relative rotation of the first rotational
shaft 42 and the second input side rotating body 52 in the first
state. The connection switching unit 62 comprises a plurality of
pawl 68 and a plurality of engagement portion 70. Preferably, a
plurality of the pawls 68 and a plurality of the engagement
portions 70 are provided. However, only one of the pawls 68 and one
of the engagement portions 70 can be provided. The pawls 68 are
disposed between the outer perimeter of the first rotational shaft
42 and the inner perimeter of the second input side rotating body
52. The pawls 68 can protrude from the first rotational shaft 42.
The engagement portion 70 is provided so that the pawls 68 is
engaged with the second input side rotating body 52. The connection
switching unit 62 connects the first rotational shaft 42 and the
second input side rotating body 52 the pawls 68 engaging the
engagement portions 70. The connection switching unit 62 permits a
relative rotation of the first rotational shaft 42 and the second
input side rotating body 52 by separating the pawls 68 from the
engagement portions 70. The engagement portions 70 comprises one or
a plurality of recesses and/or protrusions. The engagement portions
70 can be formed by a ratchet groove.
The actuator 66 controls the connection switching unit 62. The
actuator 66 comprises a biasing member 72, a movable member 74 and
a drive unit 76.
The biasing member 72 applies force to the pawls 68 so that the
pawls 68 protrude from the first rotational shaft 42. The biasing
member 72 is, for example, an annular spring, that is attached to
the outer perimeter part of the first rotational shaft 42 so as to
cover a part of the pawls 68.
The movable member 74 is configured to cause the pawls 68 to
operate with respect to the second input side rotating body 52 so
that the pawls 68 move away from the engagement portions 70. The
movable member 74 is an annular member that is supported in the
housing 40 around the first rotational shaft 42 so as to be
relatively rotatable with the first rotational shaft 42. The
movable member 74 is provided in a position in which the first end
surface 74A thereof in the axial direction opposes the pawls 68.
The first end surface 74A is formed in a tapered shape in which the
diameter increases toward the pawls 68. The movable member 74 is
biased in a direction away from the pawls 68 in the axial direction
by, for example, a spring.
The drive unit 76 switches between the first state and the second
state by moving the movable member 74. The drive unit 76 comprises
a shifting motor 78 and an annular member 80. The annular member 80
is supported in the housing 40 around the first rotational shaft 42
so as to be relatively rotatable with respect to the first
rotational shaft 42. The annular member 80 comprises a cam surface
80A on an end face in the axial direction. The movable member 74 is
in contact with the cam surface 80A of the annular member 80.
The cam surface 80A is configured to come in contact with a second
end 74B of the movable member 74 in the axial direction. The
annular member 80 is connected to the shifting motor 78 and can be
rotated by the shifting motor 78. When the annular member 80 is
rotated by the drive of the shifting motor 78, the movable member
74 is moved in a direction approaching the pawls 68, or in a
direction away from the pawls 68, depending on the rotational
direction of the annular member.
The one-way clutch 64 is provided between the first rotational
shaft 42 and the first input side rotating body 50. The one-way
clutch 64 integrally rotates the first rotational shaft 42 and the
first input side rotating body 50 when the rotational speed of the
first input side rotating body 50 in the first rotational direction
is equal to the rotational speed of the first rotational shaft 42.
The one-way clutch 64 allows relative rotation of the first
rotational shaft 42 and the first input side rotating body 50 when
the rotational speed of the first input side rotating body 50 in
the first rotational direction is greater than the rotational speed
of the first rotational shaft 42. When the second state is formed
by the connection switching unit 62, the rotation of the second
input side rotating body 52 is transmitted to the second output
side rotating body 56. In this case, the rotational speeds of the
output unit 58 and of the first output side rotating body 54 are
higher than when the rotation of the first input side rotating body
50 is transmitted to the first output side rotating body 54.
Accordingly, the rotation of the first output side rotating body 54
rotates the first input side rotating body 50 at a higher speed
than the first rotational shaft 42. Accordingly, the rotational
speed of the first input side rotating body 50 becomes higher than
the rotational speed of the first rotational shaft 42, and the
first input side rotating body 50 and the first rotational shaft 42
are allowed to relatively rotate by the one-way clutch 64. The
first rotational direction is the rotational direction of the first
input side rotating body 50 when the electrically assisted bicycle
10 moves forward.
As shown in FIG. 2, when the movable member 74 approaches the pawls
68 and is rotating the pawls 68 around the first rotational shaft
42, the pawls 68 are spaced away from the engagement portions 70.
Accordingly, relative rotation of the first rotational shaft 42 and
the second input side rotating body 52 is permitted. Accordingly,
the rotational speed of the first rotational shaft 42 is changed
according to the ratio of the total number of teeth of the gear 50A
of the first input side rotating body 50 relative to the total
number of teeth of the gear 54A of the first output side rotating
body 54. The total number of teeth of the gear 50A is less than the
total number of teeth of the gear 54A.
As shown in FIG. 3, when the movable member 74 is spaced away from
the pawls 68, the pawls 68 protrude toward the engagement portions
70 by the biasing member 72. At this time, since the pawls 68 are
engaged with the engagement portions 70, it is possible to
integrally rotate the first rotational shaft 42 and the second
input side rotating body 52. Accordingly, the rotational speed of
the first rotational shaft 42 is changed according to the ratio of
the total number of teeth of the gear 52A of the second input side
rotating body 52 relative to the total number of teeth of the gear
56A of the second output side rotating body 56. Since the total
number of teeth of the gear 52A is equal to or less than the total
number of teeth of the gear 56A, the rotation of the first
rotational shaft 42 is transmitted to the second output side
rotating body 56 at a constant speed or after being decelerated.
Additionally, the ratio of the rotational speed of the first output
side rotating body 54 relative to the rotational speed of the first
input side rotating body 50 is greater than the ratio of the
rotational speed of the second output side rotating body 56
relative to the rotational speed of the second input side rotating
body 52. Accordingly, when in the first state shown in FIG. 2, the
rotation of the first rotational shaft 42 is decelerated more than
when in the second state shown in FIG. 3 and transmitted to the
first output side rotating body 54 and the second output side
rotating body 56.
The drive unit 30 further comprises a torque sensor 82 and a
rotational speed sensor (not shown). The torque sensor 82 is, for
example, a strain gauge, a semiconductor strain sensor, or a
magnetostrictive sensor. The torque sensor 82 is attached to the
output unit 58. The torque sensor 82 is configured to detect torque
that is applied to the output unit 58.
When the rotation of the crankshaft 32 is transmitted to the output
unit 58 and the rotation of the motor 38 is not transmitted to the
output unit 58, the torque sensor 82 outputs a signal to the
controller 46 that reflects the manual drive force that is inputted
to the crankshaft 32. When the rotation of the crankshaft 32 and
the rotation of the motor 38 are transmitted to the output unit 58,
the torque sensor 82 outputs a signal to the controller 46 that
reflects the torque obtained by combining the manual drive force
that is inputted to the crankshaft 32 and the torque of the motor
38 transmitted via the transmission 36.
The rotational speed sensor comprises a cadence sensor that detects
the rotational speed of the crank. The cadence sensor detects, for
example, a magnet that is provided on the crankshaft 32. The
cadence sensor comprises a magnetism detection sensor, such as a
reed switch or a Hall Effect element. The cadence sensor outputs a
signal corresponding to the rotational speed of the crankshaft 32
to the controller 46. The cadence sensor can also be configured to
detect a magnet that is provided to the crank arms 12. In this
case, the cadence sensor outputs a signal to the controller 46
corresponding to the rotational speed of the crank arms 12. The
rotational speed sensor can further comprise a speed sensor that
detects the rotational speed of the front wheel or the rear wheel
of the electrically assisted bicycle 10. The controller 46 is
programmed to calculate the rotational speed of the crank based on
the detection result of the rotational speed sensor.
The controller 46 controls the motor 38 and the shifting motor 78.
The controller 46 controls the rotation of the motor 38 and the
rotation of the shifting motor 78 according to the manual drive
force and the rotational speed of the crankshaft 32. In one
example, the controller 46 controls the outputs of the motor 38 and
the shifting motor 78 based on the manual drive force that is
detected by the torque sensor 82, and the travel speed of the
electrically assisted bicycle 10 that is detected by the rotational
speed sensor.
When the rotational speed of the crank becomes higher than a
predetermined speed from equal to or less than the predetermined
speed, the controller 46 drives the shifting motor 78 to engage the
first rotational shaft 42 with the second output side rotating body
56. When the rotational speed of the crank becomes lower than a
predetermined speed from equal to or greater than the predetermined
speed, the controller 46 drives the shifting motor 78 to release
the engagement of the first rotational shaft 42 and the second
output side rotating body 56. Accordingly, the ratio of the
rotational speed of the output unit 58 relative to the rotational
speed of the first rotational shaft 42 becomes relatively large in
the region in which the rotational speed of the crank is high, and
the ratio of the rotational speed of the output unit 58 relative to
the rotational speed of the first rotational shaft 42 becomes
relatively small in the region in which the rotational speed of the
crank is low.
The rotation, the speed of which is changed by the transmission 36,
is transmitted to the output unit 58. That is, the torque of the
motor 38 and the torque of the crankshaft 32 are combined in the
output unit 58. By such a configuration, only the torque of the
motor 38 is transmitted from the first input side rotating body 50
and the second input side rotating body 52 to the output unit 58,
and the torque that is output from the output unit 58 is joined
with the manual drive force in a transmission path of the drive
force from the output unit 58 to a wheel (not shown) that is
connected to the rear sprocket 20 (refer to FIG. 1). The output
unit 58 is configured to receive only torque from the motor via the
first input side rotating body 50 and the second input side
rotating body 52. The first input side rotating body 50 and the
second input side rotating body 52 are configured to transmit only
torque from the motor 38 to the output unit 58. The rotation of the
transmission 36 is transmitted to the front sprocket 18, and the
rotation of the crankshaft 32 is applied thereto without
interposing the transmission 36.
The action and effects of the drive unit 30 will be described.
(1) The drive unit 30 comprises the transmission 36 that changes
the rotational speed of the motor 38 and transmits the rotation of
the motor 38 to the output unit 58. It is possible to change the
transmission ratio of the transmission 36 by driving the shifting
motor 78. According to this configuration, it becomes easy to
suppress the rotational speed of the motor 38 to within a
prescribed range; therefore, it is possible to prevent a reduction
in the assisting force accompanying a. change in the rotational
speed of the crank.
(2) The motor 38 is partially disposed on the same plane as the
first input side rotating body 50 and the second input side
rotating body 52, wherein the plane is perpendicular to the first a
rotational axis CA and the second rotational axis CB. Accordingly,
the size of the drive unit 30 in the axial direction of the
crankshaft 32 can be reduced.
(3) The switching mechanism 60 comprises the one-way clutch 64.
Therefore, the configuration of the drive unit 30 can be
simplified, compared to a case in which a connection switching unit
62 is provided between the first input side rotating body 50 and
the first output side rotating body 54, in the same manner as the
second input side rotating body 52 and the second output side
rotating body 56.
MODIFICATIONS
The descriptions relating to the embodiment described above are
examples of forms that the bicycle drive unit according to the
present invention can take and are not intended to limit the forms
thereof. The bicycle drive unit according to the present invention
can take the forms of modifications of the above-described
embodiment shown below, as well as forms that combine at least two
modifications that are not mutually contradictory.
The configuration of the drive unit 30 of the embodiment can be
freely changed, as shown in, for example, FIG. 4. in the drive unit
30 of FIG. 4, the output unit 58 is formed by the crankshaft 32. In
this configuration as well, only the torque of the motor 38 is
transmitted from the first input side rotating body 50 and the
second input side rotating body 52 to the output unit 58, and the
torque that is output from the output unit 58 is joined with the
manual drive force in a transmission path of the drive force from
the output unit 58 to a wheel (not shown) that is connected to the
rear sprocket 20 (refer to FIG. 1).
The pawls 68 of the switching mechanism 60 of the embodiment can be
allowed to protrude from the second input side rotating body. In
this case, the engagement portions 70 are provided so that the
pawls 68 are hooked on the first rotational shaft 42.
The motor 38 of the embodiment can be disposed so as to not be on
the same plane as the first input side rotating body 50 and the
second input side rotating body 52, wherein the plane is
perpendicular to the first rotational axis CA and the second
rotational axis CB. For example, the motor 38 can be disposed so
that the entire structure of the motor 38 will be farther from the
front sprocket 18 than the first input side rotating body 50 with
respect to the axial direction of the crankshaft 32 in FIG. 2.
The transmission 36 having three or more gear shift stages can be
provided in the drive unit 30 of the embodiment. For example, a
third input side rotating body is provided around the first
rotational axis CA, and a third output side rotating body is
provided around the second rotational axis CB. In this case, the
switching mechanism 60 is configured to switch between a third
state in which the first rotational shaft 42 and the third input
side rotating body are integrally rotatable, and a fourth state in
which the first rotational shaft 42 and the third input side
rotating body are relatively rotatable.
The total number of teeth of the gear 52A of the second input side
rotating body 52 of the embodiment can be greater than the total
number of teeth of the gear 56A of the second output side rotating
body 56. In this case, when the first rotational shaft 42 and the
second output side rotating body 56 are integrally rotated, the
rotation of the first rotational shaft 42 is accelerated and
inputted to the second output side rotating body 56.
In the above-described modification, the total number of teeth of
the gear 50A of the first input side rotating body 50 can be less
than or equal to the total number of teeth of the gear 54A of the
first output side rotating body 54. In this case, when the first
rotational shaft 42 and the second input side rotating body 52 are
relatively rotated, the rotation of the first rotational shaft 42
is kept constant or accelerated, and inputted to the first output
side rotating body 54.
The first output side rotating body 54 and the second output side
rotating body 56 of the embodiment can be separately formed and
each separately provided on the output unit 58.
In the above-described modification, the switching mechanism 60 can
be provided between the output unit 58, and the first output side
rotating body 54 and the second output side rotating body 56. In
this case, the first input side rotating body 50 and the second
input side rotating body 52 are fixed to the first rotational shaft
42, and the first output side rotating body 54 and the second
output side rotating body 56 are provided on the output unit 58 so
as to be relatively rotatable. If the first input side rotating
body 50 and the second input side rotating body 52 are fixed to the
first rotational shaft 42, the motor 38 or the speed reducer 44 can
transmit torque to the teeth of a gear that forms the first input
side rotating body 50, or to the teeth of a gear that forms the
second input side rotating body 52.
In the drive unit 30 of the embodiment, the torque sensor 82 can be
attached to the crankshaft 32.
In the speed reducer 44 of the embodiment, a third rotational shaft
that reduces the rotational speed of the second rotational shaft 48
and transmits the rotation of the second rotational shaft 48 to the
first rotational shaft 42 can be provided between the second
rotational shaft 48 and the first rotational shaft 42. That is,
three or more stages of deceleration can be carried out in the
speed reducer 44.
In the drive unit 30 of the embodiment, a one-way clutch can be
provided in a transmission path between the motor 38 and the
transmission 36.
The drive unit 30 of the embodiment can take a form that does not
comprise the crankshaft 32. In this case, the crankshaft 32 as a
component of the bicycle is connected to the drive unit 30.
The drive unit 30 of the embodiment can take a form that does not
comprise the speed reducer 44. In this case, for example, the gear
42A of the first rotational shaft 42 and the gear 38B of the output
shaft 38A of the motor 38 can be engaged.
The position in which the drive unit 30 is provided can be freely
changed. In one example, the drive unit 30 can be provided in the
vicinity of the rear sprocket 20. In this case, it is possible to
configure the rear wheel hub shell as the coupling member. The
transmission 36 is coupled to the rear wheel hub shell. The
rotation of the crankshaft 32 is transmitted to the rear wheel hub
shell via the rear sprocket 20. Accordingly, the rotation of the
transmission 36 is transmitted to the rear wheel hub shell, and the
rotation of the crankshaft 32 is applied thereto without
interposing the transmission 36.
In the embodiment, the second clutch 34 can be omitted.
In the embodiment, the controller 46 can be provided outside of the
housing 40, or be provided on the frame of the electrically
assisted bicycle 10.
In the embodiment, the shifting motor 78 can be omitted. In this
case, an operating lever that can be operated by a rider, and an
annular member 80 of the drive unit 76 can be connected by a
wire.
In each embodiment, the torque sensor 82 can be configured to be
disposed between a portion of the output unit 58 that is coupled to
the crankshaft 32 via the second clutch 34, and the portion where
the first output side rotating body 54 and the second output side
rotating body 56 are connected. In this case, the torque sensor 82
is able to detect only the manual drive force, even when the motor
38 being driven.
In understanding the scope of the present invention, the term
"comprising" and its derivatives, as used herein, are intended to
be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. Also, the terms
"part," "section," "portion," "member" or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts unless otherwise stated.
Also it will be understood that although the terms "first" and
"second" may be used herein to describe various components these
components should not be limited by these terms. These terms are
only used to distinguish one component from another. Thus, for
example, a first component discussed above could be termed a second
component and vice versa without departing from the teachings of
the present invention. The term "attached" or "attaching", as used
herein, encompasses configurations in which an element is directly
secured to another element by affixing the element directly to the
other element; configurations in which the element is indirectly
secured to the other element by affixing the element to the
intermediate member(s) which in turn are affixed to the other
element; and configurations in which one element is integral with
another element, i.e. one element is essentially part of the other
element. This definition also applies to words of similar meaning,
for example, "joined", "connected", "coupled", "mounted", "bonded",
"fixed" and their derivatives. Finally, terms of degree such as
"substantially", "about" and "approximately" as used herein mean an
amount of deviation of the modified term such that the end result
is not significantly changed.
While only selected embodiments have been chosen to illustrate the
present invention, it will be apparent to those skilled in the art
from this disclosure that various changes and modifications can be
made herein without departing from the scope of the invention as
defined in the appended claims. For example, unless specifically
stated otherwise, the size, shape, location or orientation of the
various components can be changed as needed and/or desired so long
as the changes do not substantially affect their intended function.
Unless specifically stated otherwise, components that are shown
directly connected or contacting each other can have intermediate
structures disposed between them so long as the changes do not
substantially affect their intended function. The functions of one
element can be performed by two, and vice versa unless specifically
stated otherwise. The structures and functions of one embodiment
can be adopted in another embodiment. It is not necessary for all
advantages to be present in a particular embodiment at the same
time. Every feature which is unique from the prior art, alone or in
combination with other features, also should be considered a
separate description of further inventions by the applicant,
including the structural and/or functional concepts embodied by
such feature(s). Thus, the foregoing descriptions of the
embodiments according to the present invention are provided for
illustration only, and not for the purpose of limiting the
invention as defined by the appended claims and their
equivalents.
* * * * *